(1) Field of the Invention
This invention relates to an image sensing head using optical fibers.
(2) Description of the Prior Art
In this type of image sensing head, image sensing end portions of optical fibers are exposed at one side of the image sensing head which is positioned against one surface of a document. End portions of the optical fibers on light emitting and light receiving sides are exposed to an opposite side of the image sensing head, with light emitting elements being connected to the end portions of the optical fibers on the light emitting side and light receiving elements being connected to the end portions of the optical fibers on the light receiving side. Light beams emitted by the light emitting elements are transmitted via the optical fibers on the light emitting side and irradiate sensed points on the surface of the document from the image sensing end portions of the optical fibers on the light emitting side. Light beams reflected by the sensed points on the surface of the document are condensed by the image sensing end portions of the optical fibers on the light receiving side. In the image sensing head of the construction described hereinabove, there are two requirements that should be met. One of them is that since the clearance between the image sensing end portions of the optical fibers and the one surface of the document has an important role in improving the performance of the image sensing head, the clearance should be considered an important factor. The other requirement is that, to avoid irregular emission of light beams emitted from the image sensing end portions of the optical fibers to the sensed points and irregular reflection of light beams reflected by the sensed points, it is necessary that the image sensing end portions of the optical fibers be polished to achieve a mirror surface finish.
To meet the two requirements noted hereinabove, it has hitherto been the usual practice to polish the image sensing end portions of the optical fibers after the image sensing head is formed, then to firmly secure a spacer to one side of the image sensing head, and thereafter to polish the surface of the spacer facing the document so as to bring the one surface of the document and the surface of the spacer facing the document to a condition in which they are parallel to each other while being spaced apart from each other by a predetermined clearance. The operation described hereinabove is not only time-consuming and troublesome but increases the costs involved because of the need to polish the image sensing end portions of the optical fibers and the surface of the spacer.